During the design and manufacture of semiconductor devices, oftentimes debug and validation processes occur in which a prototype semiconductor device is subjected to various electrical and other testing to ensure desired performance. One such testing mode that is used in advanced semiconductor devices includes optical testing implemented with a solid immersion lens (SIL), which receives optical energy emitted from the semiconductor device during injection of high speed electrical signals into the semiconductor device.
A solid immersion lens (SIL) requires direct contact with the silicon die to allow probing using a prober tool to debug and validate a semiconductor device. Providing an adequate thermal management solution to maintain maximum die temperatures between −10° Celsius (C) and 110° C. at core peak power densities of greater than 500 watts per square centimeter (W/cm2) is a very challenging task for the following reasons. First, thermal heat spreading from circuitry such as processor cores is inhibited by removing an internal heat sink and thinning the die from 700 microns (um) to between 10 and 100 um. Second, the SIL lens form factor occupies 90% of the volume that could be used for heat removal via conduction, convection, or boiling. The SIL lens must move around the die, preventing any use of a heat sink attached on a backside of the die. Third, the thermal environment is expected to get worse as power densities are anticipated to exceed 560 W/cm2 of total die power.
Cooling solutions to date have used a spray coolant flow pattern that begins at the outer edges of the die and converges to a stagnant pool of liquid across the middle of the die, called the stagnation zone. This stagnation zone surrounding the lens itself exhibits poor convective heat transfer coefficients and results in high die temperatures and large die thermal gradients near the lens.